Hinges are subject to weathering, daily wear and abuse over the years, leading to eventual failure. Outdoors they rust and are subject to being removed for unauthorized entry by the simple expediency of pulling the pins. When the pins are removed or stolen, they are often replaced by nails or other stop-gap means, resulting in their less than optimal performance.
Most outdoor hinges do not have a self-closing feature, and most that do close with a weighted rope on a pulley or with a spring. The vast majority of gates and even more doors have lo no self-closing feature at all despite the many cases in which clearly either the open or the closed position should be established as the default mode, especially when infants and small children are about.
Hinges have been designed which are self-closing, and there are also hinges assembled from two identical halves. Most require a separate hinge pin and some have structure which avoids the use of a pin. However, often these are not designed for outdoor use, and no known one-piece hinge is automatically self-closing
Some are made of plastic or nylon rather than metal, and thus avoid the corrosive effects of weather over time. By and large however, they require the use of additional structure to make a complete unit, such as a hinge pin or a clip to hold the halves together. Or, alternatively there is a one-piece hinge of the "living hinge" variety, having a limited life as at the bend line of the material is repeatedly worked back and forth until it parts.
There is a need for a weatherproof, durable, simply and rugged hinge made from two identical parts that require the use of no additional structure, the two parts of which axially migrate with respect to one another when mutually rotated such that a swing-closed feature is inherent in the design without additional components.